1. Field of the Invention
The present invention relates to a tool holding device which finds particular application in dentistry and which may be specifically designed to support very small tools such as nerve extractors, drill pins, dental cement insertion tools, screwdrivers, and the like.
2. Description of the Prior Art
The use of nerve extractors is a very delicate operation by virtue of the small size of the instrument and also because the dentist is required to hold the extractor between his thumb and index finger which obstructs the patient's mouth such that the dentist cannot see clearly.
By virtue of the fact that the instruments used slip from the dentist's fingers, there is a risk that the patient will swallow the instruments. Therefore, instruments of the kind used have been connected to small chains integral with a ring placed on the dentist's finger. While such a device serves to eliminate the risk of the patient swallowing the device, the arrangement necessarily impedes the dentist's work.
A tool holder has been suggested which comprises a rectilinear handle having one end fitted with an operating knob which drives a shaft journalled in the handle. The free end of the shaft has a pinion which interacts with a pinion of a head adapted to accommodate the tool such that the tool extends perpendicularly to the handle. A device of this type is described, in detail, in French Pat. No. 679,898, Aug. 5, 1929, and suffers from several drawbacks. In a device disclosed in the patent, the practitioner holds the handle by gripping a portion near the tool head between his index finger and his thumb. The handle rests, at one end, on the edge of the middle finger, and at the other end on the outer part of the hand extending between the index finger and the thumb. The knob must, therefore, be operated with the other hand, such that work performed with the tool holder is inaccurate because operation of the knob with the other hand causes the tool holder to move.
German Pat. No. 876,136, July 8, 1949, to a certain extent overcomes the drawback of the previously discussed device, by substituting a side knob situated in an intermediate portion along the handle for the operating knob. Such an arrangement enables the tool head to be manipulated by the index finger of the hand in which the tool is held thus resulting in far greater precision.
The device of the German patent comprises a handle having two parts which may form an angle between them. One of the parts comprises the operating knob along its side and is rotatable along its longitudinal axis with relation to the other part of the handle. Such an arrangement normally permits the user's hand to exercise full control over the tool holder whatever the direction in which the tool is being operated. Nevertheless, in reality, a device of this type is not practical since in order to operate on the upper teeth, the user must an uncomfortable position.
French Pat. No. 1,583,476 describes a manual instrument comprising a rectilinear handle provided at one of its ends with an adjustable head linked by a kinematic connection to an operating knob situated at the other end of the handle. The kinematic connection comprises a milled nut extending through an aperture provided in the handle at a point along its length such that the portion of the tool head which receives the tool itself can be rotated either at the end of the handle or by means of the intermediate nut.
Such a device is not practical in that it cannot be firmly held by the user. In operation, the holder must be held with the various fingers of the hand against the palm while the thumb is used to operate the intermediate nut.
When used, it has been found that the movements exerted by the thumb for rotating the nut cause the hand itself to move such that the operation being performed lacks precision.